In an optical disk apparatus, light emitted from a light source, after being irradiated on a disk, is led into a photodetector and converted by this photo detector into a reproduction signal, a tracking error signal for leading the light spot in a proper track, and a focus error signal for focusing the light spot in a proper position.
However, a portion of the light emitted from the light source is reflected by the optical system inside the optical pickup, by the holders sustaining this optical system and other components of the system. This portion of light thus becomes stray lights having no relation to light used with the recording and the reproduction of information.
Since the light intensity distribution of these stray lights is irregular, the photodetector cannot produce an accurate tracking error signal and focus error signal when receiving these stray lights.
Hence, conventional optical disk apparatus assume to that the amount of stray light is almost proportional to the light emission of the light source, and and compensate for error due to stray lights by subtracting a correction signal generated based on the light emission from the output signal of the photodetector,.
Such an optical disk apparatus is provided, for example as shown in FIG. 4, with servo signal correction means 21.
In the servo signal correction means 21, a photodetector 22 receives reflected light from a disk, not shown, and releases servo signals for generating a tracking error signal and a focus error signal, as well as, if stray lights are received, an error signal which becomes an error of the servo signals.
On, a light emission signal, which corresponds to the light emission of a light source, not shown, is released by a light emission detection circuit 24, and is attenuated based on a prescribed gain by a correction signal generating circuit 23 which then releases a resultant correction signal.
The correction signal is subtracted in a subtracter 25 from the above-mentioned error signal, which is then released as a corrected error signal. Thereafter, this corrected error signal is converted into a detection signal in a corrected error signal detection circuit 26, and is supplied to the correction signal generating circuit 23.
In the correction signal generating circuit 23, the gain is adjusted according to the above-mentioned detection signal from the light emission detection circuit 24, and the light emission signal is attenuated based on this adjusted gain. Thus a correction signal is generated again. The gain is adjusted likewise repeatedly, and the value of the gain at the time the corrected error signal equals 0, is held.
At time of the recording or reproducing information, a correction signal generated based on the gain adjusted in the above-described manner, is subtracted from each of the servo signals in the subtracter 25. Then, resultant signals are released as corrected servo signals and converted into a tracking error signal and a focus error signal.
In the conventional optical disk apparatus described above, gain is adjusted while a disk is installed in the apparatus. The photodetector 22 only receives reflected light from the disk. Therefore, the photodetector 22 is unable to produce an error signal compensating for the stray lights, and the adjustment of the gain in accordance with the error signal for stray lights can not be effectuated in the correction signal generating circuit 23.
Further, since described above, as an optimum gain can not be obtained, the conventional optical disk apparatus can effectively correct the servo signals.